Washington (CNN) -- President Obama wrote a personal letter to North Korean leader Kim Jong Il that a U.S. envoy delivered, a senior U.S. official said Wednesday.

Stephen Bosworth, U.S. special envoy for North Korea, delivered the letter for the North Korean leader during a three-day visit to North Korea last week, the official said.

The official declined to be identified because of the sensitivity of the issue.

Bosworth noted last week that, during his visit, he "communicated President Obama's view that complete denuclearization of the Korean Peninsula is a fundamental undertaking of the six-party process ... and that the absence of progress on denuclearization is an obstacle to improving our relations."

As Obama "has made it clear, the United States is prepared to work with allies [and] partners in the region to offer ... North Korea a different future," he said.

Bosworth also said he wanted to reaffirm the goal of "fully implementing" a September 2005 joint statement issued by the nations in the six-party talks, declaring that North Korea had "committed to abandoning all nuclear weapons and existing nuclear programs."

North Korea, however, has refused to return to the talks conducted by the United States, Russia, China, South Korea and Japan, insisting that it wants to talk directly with the U.S. government.

Video: Engaging with North Korea

In April, Pyongyang declared the talks "dead" in anger over international criticism of its nuclear and missile tests this year.

Bosworth's visit did not result in any promise from the North Korean government to return to the six-party negotiations aimed at ending its nuclear program. Secretary of State Hillary Clinton, however, last week called the meeting "quite positive."

"It does remain to be seen whether and when the North Koreans will return to the six-party talks, but the bottom line is that these were exploratory talks, not negotiations," she said.

Clinton previously said the United States was willing to meet bilaterally with North Korea but only within the framework of the six-party talks. She also has warned the United States will not normalize ties with Pyongyang or lift sanctions unless North Korea takes irreversible steps toward dismantling its nuclear program.

Some analysts said North Korea might be trying to buy time with its new outreach to the United States. Recent reports in Seoul, South Korea, have claimed North Korea is in the final stages of restoring its Yongbyon nuclear plant, which Pyongyang had begun to disable before walking away from the six-party talks.

Given the secrecy of the North, those reports could not be verified.

Analysts said North Korea also is desperate to break out of its diplomatic isolation and ease its economic pain, especially after the U.N. Security Council imposed tougher sanctions on the country in response to Pyongyang's nuclear and missile tests.